Post on 15-Apr-2017
Spectral Sensitivity of Cones of the Monkey Macaca Fascicularis. Baylor et al. 1987
Phanith & Mathew
Breakdown into Vision Three classes of cones Microspectrophotometry (MSP) Direct photocurrent measurement Wavenumber = 1/λ
AIM
To build upon currently known cones spectral sensitivities by determining the sensitivities of
cones to a broader range of wavelengths.
Phototransduction
Kandel
Phototransduction
Kandel
Suction electrode technique Outer segment of cone =
phototransduction
Measured responses to: 440 nm 500 nm 659 nm
Fractional bleaching f = 1 – e-I*A
1. Spectral Sensitivities (Methods)
opsin opsin* opsinbleached
retinaltrans
retinalcis pigment epithelium
phototransductioncascade
2. Spectral Forms Principle of Univariance
Probability of photon absorption determined by wavelength
Amplitude and waveform of response independent of photon wavelength
2 Photon Response
What is the importance of the Principle of Univariance?
Principle of Univariance
Figure 1. Figure 2.
exponential saturation function:
r = rm(1-e-ki)
r = peak amplitude of the responserm = maximal amplitudei = flash photon density
Principle of Univariance
Figure 1. Figure 2.
exponential saturation function:
r = rm(1-e-k(λ)i)
r = peak amplitude of the responserm = maximal amplitudei = flash photon densityk(λ) = proportionality constant
S
3 & 4. Maximum Sensitivities and Fitting
M LLegend:
6th order polynomial:
Figure 3a. Figure 3b.
Limitations:• Top region is flat
• True shape must be assumed
5. Subclasses of Cones Linear regression Derived from:
15 L cones from 6 macaques 19 M cones from 7 macaques 4 S cones from 3 macaques
5. Subclasses of Cones
Figure 1. The genetics of normal and defective color vision. Neitz 2011
6. Psychophysical Results
Figure 4.
λ𝑥=645nmλ 𝑦=526 nmλ𝑧=444 nm
Monitor and Cone Spaces
Cone Isolating Stimuli
Comparisons of Spectra estimate of human cones
spectral sensitivities note:
smooth curve = Π mechanisms points = adjusted sensitivity
points
adjusted for: macular pigment lens screening
L
M
S
Discussion: